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fix: liberal parsing of zero scale decimals #8700

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fix: liberal parsing of zero scale decimals #8700

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25bc45c
fix: liberal parsing of zero scale decimals
gruuya Oct 23, 2025
446400d
Update arrow-cast/src/parse.rs
gruuya Oct 24, 2025
124441b
fix: extend test cases
gruuya Oct 24, 2025
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28 changes: 28 additions & 0 deletions arrow-cast/src/parse.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -963,6 +963,14 @@ pub fn parse_decimal<T: DecimalType>(
}

if !is_e_notation {
if scale == 0 && fractionals > 0 {
// The input string contained some fractional digits after the decimal point despite
// the scale being zero. Eject all the fractional digits from the number.
result = result.div_wrapping(base.pow_wrapping(fractionals as _));
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Would this be correct if there are many fractional digits, e.g. 20+ ?!

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I think it would, added another test case on that note (("123.000000000000000000004", 123)).

digits -= fractionals as u8;
fractionals = 0;
}

if fractionals < scale {
let exp = scale - fractionals;
if exp as u8 + digits > precision {
Expand Down Expand Up @@ -2636,6 +2644,7 @@ mod tests {
("12345678908765.123456", 3),
("123456789087651234.56e-4", 3),
("1234560000000", 0),
("12345678900.0", 0),
("1.23456e12", 0),
];
for (s, scale) in overflow_parse_tests {
Expand Down Expand Up @@ -2752,6 +2761,25 @@ mod tests {
let result = parse_decimal::<Decimal256Type>(s, 76, scale);
assert_eq!(i, result.unwrap());
}

let zero_scale_tests = [
("0.123", 0),
("1.0", 1),
("1.2", 1),
("1.00", 1),
("1.23", 1),
("1.000", 1),
("1.123", 1),
("123.0", 123),
("123.4", 123),
("123.00", 123),
("123.45", 123),
("123.000000000000000000004", 123),
];
for (s, i) in zero_scale_tests {
let result_128 = parse_decimal::<Decimal128Type>(s, 3, 0).unwrap();
assert_eq!(i, result_128);
}
}

#[test]
Expand Down
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